Geometry

I am re-posting this, hope one of you people can help me out. -- I am looking for a sample 3-D geometry of a semi-circular (or semi-elliptical) to circular s-duct. This could be in the form of (x,y,z) or z=f(x.y) , or any other functions.

If anybody has such a file or knows where I can find it, please let me know.

Take a look at the paper by Yang (R. Yang, S.F. Chang and W. Wu "Flow and heat transfer in a curved pipe with periodically varying curvature" Int. Comm. Heat Mass Transfer, 27, 133-143, 2000). He studies S - pipes and provides the geometric functions to define such a pipe. Which is basically a centerline sine function. You can use those functions to transform a straight circular pipe into an S-pipe.